In recent years, projectors that project an image on a screen have been widely used not only in offices but also at home. The projectors each modulate light from a light source by a light valve to generate image light, and thereafter project the image light on a screen to perform display (refer to PTL 1, for example). Recently, the projectors have been increasingly downsized, and palm-sized projectors, mobile phones with built-in projectors, and other projectors have started to be widespread.